This R03 application proposes feasibility studies in a novel model of HIV-1 infection in mice to address directly the potential role of morphine in facilitating HIV-1 entry into the brain and viral effects on the tissue. We showed that normal inbred mice can be "naturally" infected with a chimeric HIV-1 carrying ecotropic MLV envelope, termed EcoHIV. Kinetic studies of this infection revealed an initial burst of virus replication in peripheral T cells and macrophages within 1 week, followed by virus persistence at lower levels, induction of antiviral immune responses, virus neuroinvasion, and a number of changes in the brain but no other major indicators of disease during several weeks of follow up. These characteristics resemble the asymptomatic stage of HIV-1 infection in humans or SIV infection in macaques. Interestingly, EcoHIV expression and changes in the brain are delayed compared to systemic infection. The delay likely represents the time (and processes) required for the virus to breach the blood brain barrier (BBB) and establish brain infection. The HIV-1-mediated brain disease in people is also secondary to systemic infection and it closely correlates with influx of HIV-1-infected macrophages into the CNS and neuroinflammation. Drugs of abuse such as morphine are believed to exacerbate HIV-1 neuropathogenesis, among others by facilitating transit of HIV-1 or infected cells through the BBB. We believe that the EcoHIV-mouse model gives us a unique opportunity to address elements of this hypothesis in direct experimentation in vivo. [unreadable] Here we will attempt to answer two discrete questions on the possible functional relationship between morphine administration and EcoHIV infection in mice: 1) Does morphine treatment facilitate the course of EcoHIV infection, neuroinvasion, and early molecular changes in mouse brains? We will use wild type and mu opioid receptor knock out mice and determine kinetics of systemic EcoHIV infection, virus entry and expression in the brain, and expression of MCP-1 and IL-1beta in brain tissue as early markers of brain pathology; 2) Does morphine enhance BBB permeability to large molecules and cells in EcoHIV- infected animals? Under optimal conditions established in Aim 1, we will determine uptake of labeled albumin and trans-endothelial migration of macrophages into mouse brain. The proposed project utilizes a novel small animal'model of HIV-1 infection to address a critical public health issue of the potential contribution of drugs of abuse in exacerbating the consequences of HIV-1 infection. The studies will combine interdisciplinary expertise in drug abuse research, HIV-1 biology, brain research, and animal models from two laboratories and they should shed new light on the relationship between drug abuse and HIV-1 disease. [unreadable] [unreadable] [unreadable]